Background: I have an '87 with the 4.2l I6/NP207 combo and I'm wanting to swap it for an AX15/NP231 combo.
1) What year AX15 (if there's any specific) will I need to get that will bolt to the '87 4.2?
2) Will I need to change the pilot bearing? If so, which one?
3) Will I need to change the clutch or flywheel? If so, which one?
4) Will I need to change the starter? If so, which one?
5) Will I need new mounts for the AX15/NP231?
6) Am I forgetting anything?
There's a couple of fantastic write-ups on this swap if you google it.
Basically, using the 4.2 flywheel & clutch for your year 4.2:
a 90-91 donor is a virtual bolt in using the 4.2 clutch, ax-15, bellhousing & attached Tcase. Pilot is the same (tho I replaced mine along w/ clutch), only have to drill new holes in skid plate to mount the trans (AX-15 mount). Even the speedo cable works fine.
Later versions of the AX-15 w/ big pilotshaft tip need a new pilot bushing (from CJ w/ 304) & may have a different speedo drive depending on year. If they are a 94-up, then they will need a different hydraulic line for the external slave cylinder too.
The starter remains the same.
It helps immensely to get the whole shebang from bellhousing to Tcase (including shifters/linkage!) from one donor. My 91 donor bolted right up, driveshafts & all.